Add ScopedKeepAlive to c/b/lifetime

chrome/browser/lifetime/keep_alive_registry.h

+// Copyright 2016 The Chromium Authors. All rights reserved.
+// Use of this source code is governed by a BSD-style license that can be
+// found in the LICENSE file.
+
+#ifndef CHROME_BROWSER_LIFETIME_KEEP_ALIVE_REGISTRY_H_
+#define CHROME_BROWSER_LIFETIME_KEEP_ALIVE_REGISTRY_H_
+
+#include <map>
+
+#include "base/macros.h"
+#include "base/memory/singleton.h"
+
+enum class KeepAliveOrigin;
+
+class KeepAliveRegistry {
+ public:
+  static KeepAliveRegistry* GetInstance();
+
+  bool WillKeepAlive() const;
+
+ protected:
+  KeepAliveRegistry();
+  virtual ~KeepAliveRegistry();
+
+  // Prevent the browser from closing. Called when a KeepAlive is first
+  // registered.
+  virtual void HugBrowser();

[sky, 2016/02/25 00:25:18]

'hug', eh? How about PinBrowser(), PreventBrowserFromClosing().

[dgn, 2016/02/25 17:19:46]

Removed, since I'm not mocking the method anymore.

+
+  // Let the browser close. Called when the last KeepAlive is unregistered.
+  virtual void ReleaseBrowser();

[sky, 2016/02/25 00:25:18]

I'm not a fan of virtual functions like this just for testing (especially when
that testing involves gmock).
Seems like your tests can be covered by calling WillKeepAlive(). Do you really
need the virtuals here?

[dgn, 2016/02/25 17:19:46]

I wanted to check the call that has external effects and not only checking that
internal state with WillKeepAlive. So now I just exposed the keep alive count
from application_lifetime. I'll update the test when I get rid of the count
there.

+
+ private:
+  friend struct base::DefaultSingletonTraits<KeepAliveRegistry>;
+  friend class KeepAliveRegistryTest;
+  // Friend to be able to use Register/Unregister
+  friend class ScopedKeepAlive;
+
+  // Allows to provide a specific instance for testing purpose. At the end
+  // of the test, reset it by setting it to |nullptr|.
+  static void SetInstanceForTesting(KeepAliveRegistry* new_instance);
+
+  // Add/Remove entries. Do not use directly, use ScopedKeepAlive instead.
+  void Register(KeepAliveOrigin origin);
+  void Unregister(KeepAliveOrigin origin);
+
+  // Tracks the registered KeepAlives, storing the origin and the number of
+  // registered KeepAlives for each.
+  std::map<KeepAliveOrigin, int> registered_keep_alives_;
+
+  // Total number of registered KeepAlives
+  int registered_count_;

[sky, 2016/02/25 00:25:18]

You need to initialize this to 0.

[dgn, 2016/02/25 17:19:46]

Thanks. Done.

+
+  DISALLOW_COPY_AND_ASSIGN(KeepAliveRegistry);
+};
+
+#endif  // CHROME_BROWSER_LIFETIME_KEEP_ALIVE_REGISTRY_H_